From Citroen SM Wiki
The original regulator ...
- The metal cover can short out. fit a fuse to the supply wire at the top of the regulator.
Incorrect charging may be the body of the regulator is not directly connected to the battery negative (O.E. is a yellow wire). High charging can be caused by a low voltage in the regulator supply wire. First check for bad contacts elsewhere. The cover of the regulator can be removed and the charging voltage adjusted. Low charging is usually a failed diode in the alternator.
There are a number of alternatives:
- alternator with internal regulator
- Replace regulator with a modern one
- cross references...?
If you want to keep the stock appearance, you can embed a modern regulator in the old regulator can. See Regulator.pdf for one approach.
- http://www.candokaraoke.com/Regulator.pdf -- Original site for regulator embedding PDF